Thursday, 17 December 2015

Accurate predictions of the impacts of future land use change on species of conservationconcern can help to inform policy-makers and improve conservation measures. In a new paper just published in PLOS One, we introduce a method, based on open source software, which integrates habitat suitability modelling with scenario-building. We illustrate its use by investigating the effects of alternative land use change scenarios on landscape suitability for black grouse Tetrao tetrix in the Scottish uplands.

Likely changes in the uplands

The first step was to build a habitat suitability model for the species, in this case using the well-used MaxEnt. This gave a standard map of suitability for pixels across the 800 sq km landscape in Perthshire. We wanted to simulate how the upland area might change over the next 20 years so we asked upland experts how they thought the landscape might change – they told us that most likely were changes from moorland and grazed land to open canopy forestry due to native forestry planting schemes and grazed land to moorland via a reduction in grazing.

A moorland and open
woodland mix in Perthshire - a potential result of the reduced grazing scenario
which resulted in beneficial landscapes for black grouse (Photo: Matt Geary).

Growing patches of new habitat

To represent how these changes in land use would affect the area, we grew patches of new habitat within the existing landscape (e.g. new patches of open woodland where moorland currently exist). We grew the new patches using a piece of old script in Mathematica supplied by Ed Harris here at MMU, which was updated to work in R and embedded into our model. For each scenario, the cover of different land use types was altered by 5–30% from 20 random starting locations – this enabled us to look at how the amount of new habitat and its spatial positioning of the new land uses might affect their impact on the grouse. We then ran the MaxEnt again with the 20 new landscapes and assessed changes in suitability – much like people do with climate change scenarios and their effects on species ranges.

Effects of land use changes

The scenario where grazed land was replaced by moorland and open forestry was the most beneficial for black grouse, and ‘increased grazing’ (the opposite conversion) the most detrimental. Positioning of new land use blocks was shown to be very important. So it is not just a case of a certain benefit or loss brought about by a certain amount habitat change - where those habitat changes occurred was also very important. This might be helpful to local land use planners and habitat managers – habitats could be placed so as to maximise benefits for a key species, or at least to minimise their detrimental effects.

Another important finding was that, while increasing the area of open canopy forestry caused a proportional decrease in suitability, suitability gains for the ‘reduced grazing’ scenario were nonlinear. Reducing grazing slightly to create small additional amounts of moor and open canopy woodland had small benefits to grouse, but reducing it by 20% had disproportionately large benefits in terms of habitat suitability for the species. Again, this kind of result might help inform local land management and even regional policy such as grant schemes promoting land use changes.

This ‘Scenario-led’ landscape simulation modelling can be applied in assessments of the impacts of land use change both on individual species but also on diversity and community measures, or ecosystem services. A next step would be to include landscape configuration more explicitly in the simulation models, both to make them more realistic, and to examine the effects of habitat placement more thoroughly.

Monday, 14 December 2015

In a new research funded by the Peregrine Fund, The British Ornithological Union, The Neotropical Bird Club and MMU, MSc student Diego Mendez has shown that it is possible to individually identify Andean Condors Vultur gryphus on the basis of selected natural markings through the examination of photographs of perched and flying birds. More importantly, Diego’s research reveals that Andean Condor populations in Bolivia are still reasonably large. However, the population structure may be skewed toward male and sub-adult birds, with fewer females being present within the Bolivian population.

Between July and December 2014, Andean Condors were surveyed at 28 different locations (which we called survey feeding stations) throughout the eastern Andean region of Bolivia, encompassing the high-Andean vegetation, semi-humid puna, inter-Andean dry forest, Bolivian-Tucuman forest and Chaco Serrano ecoregions in the Cordillera Oriental and Subandino. Condors were attracted to each feeding station using equine carcasses that had been obtained humanely.

Diego at photographic blind waiting for Condors to show up.

At each feeding station, condors were photographed from 7 am to 6 pm whilst they fed at the carcasses. Photos were taken from newly constructed observation hides positioned 35-100 m from the animal carcass to permit optimal viewing of feeding and flying condors. To photograph condors, Diego and his field assistants used a digital camera mounted on a digiscoping adaptor attached to an 82 mm-objective spotting scope with a 20-60 magnification eyepiece, plus one or two bridge cameras with lenses with focal distances of up to 810-1550 mm.

The team took as many photographs as possible aiming to get high quality photographs that clearly showed both flanks of perched adult condors (head and body for males) and fully extended flying and tail feathers of condors in flight. By the end of the surveys, Diego and his team managed to take over 21,000 photographs of Andean Condors, of which nearly 8,000 (37%) were judged to be usable for condor identification.

A total of 566 condors were recorded from all survey feeding stations. From these data, Diego identified 456 different individuals, including 134 adult males, 40 subadult males, 79 juvenile males, 80 adult females, 30 sub-adult females and 93 juvenile females. Thus, the minimum population count for the Andean Condor population was 456 individuals with a population structure composing of adults, sub-adults and juveniles. Closed population capture-recapture homogeneity modelling produced a population estimate of 1,222 ± 99 (SE) condors. This estimate encompasses the population to the eastern Andes of central and southern Bolivia including the Apolobamba Mountains, an area of approximately 42,000 sq km.

The observed population structure of Andean Condors in this study is similar to those observed by Ríos-Uzeda & Wallace (2007) and Méndez et al. (2015) in that the population is slightly skewed towards adult males and immature birds (sub-adults and juveniles). These findings support a previous figure for the adult male-sewed population throughout the species’ range (Lambertucci et al. 2012). Studies of White-rumped Vulture Gyps bengalensis have also revealed male skewed sex ratios (Arshad et al. 2009), and the population structure of the California Condor Gymnogyps californianus population – a human managed population – is also slightly male skewed. These findings suggest that perhaps special attention should be allocated to sub-adult individuals to better conserve Andean Condor populations throughout their range.

Ríos-Uzeda, B. & Wallace, R.B. (2007). Estimating the Size of the Andean Condor Population in the Apolobamba Mountains of Bolivia. Journal of Field Ornithology 78: 170-175.AcknowledgementsDiego's work is
part of Proyecto Cóndor Andino - Asociación Armonía and has been
supported by

About the Research Group and blog

This blog includes posts by members of Stuart Marsden's conservation research group based in the School of Science & the Environment at Manchester Metropolitan University. The group mainly includes PhD students working on the conservation ecology of birds and other wildlife, often in the tropics. We also have posts from other collaborators and alumni.